1. Field of the Invention
This invention relates to transporting, storing, blending, and refining crude oil. This invention particularly relates to using online instruments to monitor and/or control transporting, storing, blending, and refining crude oil.
2. Background of the Prior Art
As world reserves of light, sweet crudes diminish and worldwide consumption of oil increases, refiners seek methods for extracting useful products such as gasoline and fuel oils from heavier crude resources. While not as desirable and easy to process, extensive reserves in the form of “heavy crudes” exist in a number of countries, including Western Canada, Venezuela, Russia, the United States, and elsewhere.
For example, heavy or extra heavy crude oil can be found in the Orinoco Belt in Venezuela, the oil sands in Canada, and the Ugnu Reservoir in Northern Alaska. Alberta produces approximately two-thirds of Canada's oil and more than three-quarters of its natural gas. Nearly half of Alberta's oil is mined from vast oil sands, which contain deposits of a heavy crude oil called bitumen. Alberta's oil sands represent the largest known deposits of bitumen in the world. The oil sands occur in three major areas of the province: the Athabasca River Valley in the northeast, the Peace River area in the north, and the Cold Lake region in east central Alberta.
Such heavy oils (even some not so heavy oils) are often difficult to refine because of their viscosity and propensity for being unstable and precipitating solids upon storage and processing, most notable asphaltenes. Asphaltenes are high molecular weight aromatic carbonaceous compositions, normally solid at room temperature. When they precipitate from crude oil, they can foul equipment and reduce the quality of the products being refined. Other issues associated with heavy crude oil include: high solids; increased amounts of entrained water; and high sulfur content; high total acid number (TAN) and high metals. Asphaltene deposition is a well-known problem affecting all aspects of petroleum production and processing. Crude oils containing high or low levels of asphaltenes can be destabilized while processing causing fouling, formation of sludge, corrosion and all the equipment fixing, cleaning, and cost aggravations associated with these effects.
Additional operational problems observed with heavy crude oil: difficulty in blending crude streams, increased unit upsets, increased pollution, loss of through-put, difficulty with desalting, increased load on wastewater plants, increase in air emissions, and flexibility in plant operations is reduced. All of this leads to an overall increase in operating costs. It follows that it would be desirable in the art to be able to use an online method of monitoring and predicting the stability of crude oil so that the crude oil could be more efficiently stored, transported, blended, and refined.